Communication systems, in particular wireless communication systems, utilize power amplifiers to modulate signals as part of the communication process. The power amplifiers should have certain characteristics in order to perform suitable modulation of baseband signals. This suitable modulation requires that distortions and noise are mitigated to sufficient levels.
In one example, non-linear power amplifiers are utilized for amplitude to amplitude modulation. However, amplitude to phase modulation effects can occur to yield distortions or noise in the amplitude modulation signal.
One technique to mitigate the phase modulation effects is to stimulate a non-linear power amplifier with baseband samples and then observe the result of that stimulus at the power amplifier output. Then, the amplitude to amplitude modulation and amplitude to phase modulation effects of the power amplifier are estimated. These estimated distortions are then removed from the power amplifier by pre distorting the input stimulus with their inverse equivalents.
However, there are other distortions or noise that can be introduced into power amplifiers that degrade or mitigate their performance, including modulation.